Sound recording method and system



Jan. 11, 1944. v A. L Hol-.come 2,338,766

SOUND RECRDING METHOD AND SYSTEM Filed July 16,` 1942 /Nl/ENTOR 1. L. Ho/ COMB A r Tom/5VI Jan. 11, 1944l RECORDING m01) AND SYSTEM Artlrm-'L Holcomb. Talma, Calif.. aaaignoto ew Western Elect-ic Company York, N. Y., a corporation of New' York Application July 1c, 1942, serial No. 451,133'

15 chan.. (ci. 11s-10aa) 'I'his invention relates to a method and apparatus for the automatic control 'oilevel sequences Ain the transmission of electrical currents in accordance with a predetermined schedule and* has particular reference to the electrical rerecording of sound records.

In the sound picture art it is the established practice to combine in rerecording various original sound records to provide a nal composite record to accompany the picture. Of these sound records some may be of sounds occurring simultaneously withthe action photographed, while others maybe records of sound eiects or of music recorded independently of the action. It is necessary to rehearse the separate audible reproductions of the contributing records to determine relative levels among them and the sequence of levels in each individuallyin order to produce a satisfactory nal record. When this rehearsal has been completed, usually by theioint efforts of a number of mixer operators, the ilnal record is ready to be rerecorded.

The operators memories of desired level changes are not safely relied upon to duplicate the rehearsal in tha iinal recording and cue sheets are troublesome to adhere to. Therefore,

record be made during rehearsal in accordance control'automatically the electrical reproduction of the separate records to produce the same result as would an operator faithfully following a cue sheet. An example of such automatic control is disclosed in 'United States Patent 2,279,018 to W. V'. Wolfe. So far as known, the automatic .control methods hitherto proposed all'require a control record of electric currents generated by a source external to thesound reproducing system. oscillators have been used to generate single frequency currents which are varied in frequency or in amplitude concomitantly with the hearsal. Such procedures, of course, involve an undesirable complexity of equipment.

Thus, the primary object of the present invention is to provide a novel arrangement of apparatus and method oi' operation adapted to the purtrolled after manual control during'rehearsal.Y

it has been proposed that some form of control f with the operators judgment and later used to..v

of sound records in accordance with a. predetermined schedule. It will appear from the description of the invention that no current sourceexternal to the sound system is required, Therefore, another object attained by the invention is to provide an automatic control system involving only the reproduction of the sound record itself as a source of control current, utilizing with the greatest economy known apparatus elements.

It is often desirable to revise the automatic control and a circuit is described which permits such revision without interruption of the controlledireproduction. Accordingly, another object of the invention is .to provide means for intervening -to revise the automatic, control of one reproduction without interference to other records being rerecorded at the same time.

In the accompanying drawing, which is a schematic diagram of the apparatus suitable for the practice of the invention, the details of, well- 'I'he outputs of these and of additional channels not indicatedare combined in a known manner to be jointly Vimpressed on a monitoring loudspeaker and when desired on a recorder for making the final composite record. Since channels I, 'II and III differ only in the type of sound records, it suilices to describe channel I alone,

in which the sound record to be reproduced is It is to be understood that the electrical currents in any channelv assumed to be sound iilm i.

rotor 'I of direct current motor 8. Motor l is suitably a motor similar to that disclosed .by R. M. Rowell in United States Patent 2,110,680. Its field may be that of a permanent magnet or may be p^roduced by direct current in a tleld coil a. Two rotor windings b and c are provided which may be either separate coils or a vsingle coil with an accessible center tap. A rotation pose ci automatically controlling the rerecording through 9O-degrees of the movable plates ot. volumecontrol 8 is capable of changing by more than 80 decibels the transmitted volume. so that meter movement without a restoring spring.

Likewise coupled to shaft 6 is manually operated control dial 8 which includes details to be described later,y OutputI leads I `of volume control l are connected to preliminary amplifier II,`of

which the output circuit I2 divides into three parallel branches I 8, I4. and I5.

Branch I8 is preferably as shown permanently connected to input winding I6 of transformer I1. Output winding I8 of transformer I1 is connected in the standard manner to include volume lcontrol I9 from the output of which the sound currents corresponding to all 'of channels'I, II and III are fed to monitoring amplifier and loudspeaker 20. When switch Si is closed, the composite current is also supplied to a final sound recorder 2|. It is clear that if no more than manual control is desired in the reproduction of record I the circuit so far described suffices for rehearsal and for final rerecording. Apparatus according to the invention for automatic rerecording control will now be described. A Switches Sz, S3 and S4 shown-in the drawing in their rehearsal positions are simultaneously operable under control of relay 22, the winding of' which is supplied with current by battery 28 when switch Sa is closed. Switch Ss of dial 8 is in series with switch Ss and is normallyl closed.

Switch Ss remains open during the preliminary rehearsal of the reproduction of record I, desired variations in this reproduction being effected by manipulation of the dial 9. During rehearsal switch S. is open. respectively, output circuit I4 to the input of amplifier 24 and the output circuit of amplifier 24 to volume compressor 25, whereby sound currents reproduced from film I and compressed in volume range are applied over conductors 80a to be recorded by magnets 26 on magnetic tape 21 traveling in the direction of the arrow. Tape 21 is suitably provided with perforations enabling it to be driven by sprockets 28 and 29 in synchronism'with film I. 'Magnets 26 serve both for recording and for reproducing the record on tape 21. A preferred method of making such a magnetic record is disclosed by D. E. Wooldridge in United States Patent 2,265,831. By this means an auxiliary sound record. identical except for volume compression with record I, is recorded on sion is not invariably essential. If compression is omitted, the sound record of tape 21 will be a duplicate of record I. Obviously, any other type of auxiliary record could be used. The advanta-ges of a magnetic record are that it may be ynow inoperative. At the same time switch S4.

connects output circuit I6 of amplifier II to the input of amplifier 82, the output of which is supplied through volume compressor 88 to rectifier 84. It is requisite that amplifiers 24 and 82, compressors 2l and 88 and rectiflers 8I and 84 be similar each to each. Ifv during the rerecording of record I the settings of volume control follow exactly the sequence established during re- .v hearsal, the unidirectional qutput currents from Switches Sz and Ss connect,

tape 21. As will later appear, volume compresl immediately reproduced and may be erased, as desired, to receive revisions.

rectiflers 8I and 84 will\ beat all times equal.

'Those skilled in the art will understand how 'this equality may be insured by suitable adjustment of the reproducing circuit of magnets. 26. The output circuit of rectifiers 8I and 84 are, as

shown in the drawing, permanently and oppo- `sitely connected tovcoils b and c, respectively, of

rotor 1. No currents flow in these output circuits when switch Si is open and switches S2, Si and Si are in the rehearsal position so that during rehearsal there is no torque on rotor 1. During f the second reproduction .of record I the settings of volume control 8V will automatically conformdenser plates of volume control 6 to assume the l setting at rehearsal, whereupon the controlling torque vanishes. Switch Si being closed at the same time as switch S5, the automatically con` trolled reproduction of record I is recorded by recorder 2|.

The time mg with whichv shaft s driven by motor 8 moves to annul the current differentialfrom rectifiers 8I and 84 can be made negligible by choosing for the volume control an element which is of small mass and rotates'with minimum friction. .Capacitance voltage dividers are well suited to this purpose and may be that disclosed in Fleming United States Patent 1,989,797

as shown in the drawing or the coupling 'system disclosed by L. A. Gebhard in United States Patent 1,890,034. Both of the mentioned disclosures afford control of transmitted level without irequency discrimination. In-'order that the diiferential current driving rotor 1 shall not greatly vary with the reproduction level from amplifier II, compressors 25 and 88 are designed to raise the low and intermediate levels from amplifier 24 to be only some 5 decibels lower than the highest level therefrom. By this expedient the arithmetic diierence between the outputs of rectiflers 8I and 84 for a given error of setting of volume control shaft 6 is prevented from decreasing to a value insuillcient to provide the' necessary control torque. When the torque required is small or when the volume range of the original record is narrow, compressors 25 and 83 are properly omitted. l

Should there be a need for intervening in channel I to revise the automatic control, this may be-` done as follows:

Manual control dial 8 is provided with pushbutton kept in its normal position by a spring, not shown. In this normal position, as in the diagram, switch Se is closed and switch S7 is open. The operator, desiring to alter apart of the level sequence from that decided on during rehearsal, takes hold of dial 8, depressing as he does so button 86 to open switch Se and close switch S1. Openingy St deenergizes relay .22, whereupon switches Si, Sa. and S4. return to their rehearsal position. At the same time. closing S1 energines erasing circuit It. whereby magnets 31 act to erase a portion of the auxiliary record and continue the process of erasure as long as button 3l is depressed. The situation is now exactly as during rehearsal, the reproduction is under manl ual control and magnets 26 are enabled to record the altered sequence of levels reproduced from record I. When the operator releases dial 8, the

automatic control is reestablished. Such intervention in the controlled reproduction of record l, resulting in a revised auxiliary record on tape 2l may take place in a second rehearsal during which switch Si remains open. Repeated rehearsals may be carried out until the auxiliary l record has acquired a finally satisfactory character.

It will be clear that the stated objects of the 'invention are attained by the described arrangement of apparatus and method of operation. 'Ihe rerecording of record i under automatic control is effected by a minimum number of required apparatus elements without utilizing any current source external to the sound system and provision is made for revising the control of rec-v ord l without stopping the system and without embarrassment to the simultaneous rerecording in channels II and III.l While the description and diagram show an illustrative embodiment of the invention, it is to be understood that other elements capable of performing the various required functions may be substituted for those illustratively shown. For example, instead of separate windings rotor 'I may be provided with a single winding to which are applied in opposition control an original sound record which comprises making a first electrical reproduction of said original record under manual control of reproduced volume levels, simultaneously translating said first reproduction into sound with reference to which said manual control isvdetermined and the outputs of rectiilers 3| and, While the invention has been described with particular reference to the rerecording of sound records,it is obviously applicable in any case where one desires to repeat, under automatic control, any op-v eration of electrical transmission.

What is claimed is:

l. The method of automatic control of the rerecording of an original sound record which comprises making a first electrical reproduction of said original sound record under manual control and simultaneously making an auxiliary record of said first reproduction, making a second electrical reproduction of said original sound record g under control of said auxiliary record, and making a sound record of said second reproduction.

2. The method of rerecording withautomatic control an original sound record which comprises making a rst electrical reproduction of said original record under manual control rof reproduced volume levels, simultaneously translating said first reproduction into sound with reference to which said manual control is determined and makingan auxiliary sound record with volume compression of said first reproduction; making a" said second reproduction, and making a second record of said original record in parallel with said second reproduction.

4. The method of rerecording with automatic control an original sound record which comprises the following steps: first, electrically reproducing said original record under manual control and simultaneously making an auxiliary sound record of said reproduction; second, electrically reproducing said original record under control of said auxiliary record and manually intervening to revise said auxiliary record; repeating said second step with progressive revision of said auxiliary record to a satisfactory inal form; and, inally, electrically reproducing said original record under 'control of said auxiliary record in final form and simultaneously making a record of said original record so reproduced. l

5. In a sound rerecording system, means for rerecording 'a composite record from a plurality of sound records including a reproducing chan nel individual to each of said records, control means 1in each of said channels for automatically controlling the reproduction of the sound record associated therewith independently of the other reproducing channels, said control means including an auxiliary record rerecorded from said associated sound record, means for combining the automatically controlled reproduction of said rec ords, and means for making a'record of said scum bined reproductions.

6. In a sound record reproducing system cluding a volume control means in circuit with preliminary amplier having a primary output circuit for monitoring and rerecording a reproduced sound record, means for automatically conn trolling the rerecording of said sound record including a direct current motor having a rotor coupled to said Volume control means and provided with'armature coils, a pair of additional output circuits of said preliminary amplifier, one of said additional circuits including means for making with Avolume compression an auxiliary record of said sound record, the other of said additional circuits including amplier means for reproducing with volume compression said sound record and means for rectifying the reproduction currents of said sound record, means for reproducing said auxiliary record including means for rectifying the reproduction currents of said auxiliary record, switching means selecting in a iirst switch position said one additional circuit for making said auxiilary record and selecting in a second switch position said other additional circuit simultaneously with said means for reproducing saidauxiliary record and impressing the rectilied reproduction of said auxiliary record and the rectiiled reproduction of said sound rec ord by said other additional circuit simultaneously and in opposition upon the armature coils of said rotor, and switching means for intervening to revise said auxiliary record during the reproduction thereof. Y

7. In a sound record reproducing system including a volume control means in circuit with a preliminary amplifier having a primary output circuit for monitoring and rerecording a reproduced sound record, means for. automatically controlling the rerecording of said sound record including a direct current motor having a rotor coupled to said volume control means and pro vided with armature coils, a pair of additional output circuits of said preliminary amplifier, one

of said additional circuits including means for making an auxiliary record of said sound record, the other of said additional circuits including amplifier means for reproducing said sound recducing said auxiliary record and impressing-the rectified reproduction of said auxiliary record land the rectified reproduction of said sound record by said other additional circuit simultaneously and in opposition upon the armature coils of said rotor, and switching means for intervening to revise said auxiliary record during the reproduction thereof.

8. In a sound record reproducing system including a volume control means in circuit with a preliminary amplifier having a primary output circuit for monitoring and rerecording. a reproduced sound record, means for automatically controlling the rerecording of said sound record including a direct current motor having a rotor coupled to said volum'e control means and provided with armature coils, a pair of additional output circuits of said preliminary amplifier, one of said additional circuits including means for making with volume compression an auxiliary record of said sound record, the other .of said additional circuits including amplifier means for reproducing with volume compression said sound record and means for rectifying the reproduction currents of said sound record, means for reproducing said auxiliary record including means for rectifying the reproduction currents of said auxiliary record, and switching means selecting :,asanc of said additional circuits including means tor making an auxiliary record of said sound record. the other of said additional circuits including amplifier means for reproducing said sound record and means for rectiiyin! the reproduction currents of said sound record, means for reproducing said auxiliary record including means for rectifying the reproduction currents of said auxiliary recordI and switching means selecting in a iirst switch position said one additional circuit for making said auxiliary record and selecting in a second switch position said other additional circuit simultaneously with said means for reproducing said auxiliary record and impressing the rectified reproduction of Asaid auxiliary record and the rectified reproduction of. said sound record by said other additional ciri cuit simultaneously and in opposition upon the armature coils of said rotorh in a first switch position said one additional circuit for making said auxiliary 'record and selecting in a second switch position said other additional circult'simultaneously with said means for reproducing said auxiliary record and impressing theA rectified reproduction of said auxiliary rec.- ord and the rectified reproduction of said sound record by said other additional circuit simultanei ously and in opposition upon the armature coils of said rotor.

9. In a sound record reproducing system including a volume control means in circuit with a preliminary amplifier having a primary output circuit for monitoring and rerecording a reproduced sound record, means for automatically controlling the rerecording of said sound' record including a direct current motorhaving a rotor coupled to said volume control means and provided with armature coils, a pair of additionall output circuits of said preliminary amplifier, one

rectified output of said other additional circuit simultaneously and in opposition upon the arma- 10. Apparatus for automatically controlling the reproduction of an original sound record from a sound reproducer including a volume control means in a reproducing circuit, an auxiliary sound record of said original record made during a previous reproduction thereof, means for reproducing said auxiliary record simultaneously with a subsequent reproduction ot said original record, an additional reproducing circuit of said volume control means operative during said subsequent reproduction, means for rectifying the reproduced output of said auxiliary record; means for rectifying the output o! said additionalcircuit, and means for combining in opposition said rectified outputs to regulate said volume control means during said subsequent reproduction in accordance with said auxiliary record.

11. Apparatus as in claim -10,L including means for intervening during said subsequent reproduction to revise said auxiliary record. v

12. In an electrical transmissionA system including a volume control means in circuitwith a preliminary amplifier having a primary output circuit including monitoring means, means for the automatic control of the transmission of said primary circuit in accordance with a schedule determined in preliminary monitoring including a direct current motor having a rotor coupled to said volume control means and provided with armature coils,.a pair of additional output circuits in said preliminary, ampliiier, one of said additional circuits including means for making with volume compression an auxiliary record of said preliminary monitoring, the other of said additional circuits including amplifying means for reproducing with volume compression the output of said preliminary amplifier and for rectifying said output, means for reproducing said auxiliary record including means for rectifying the currents reproduced from said auxiliary record, switching means selecting in a first switch multaneously with said means for reproducing said auxiliary record and impressing the rectified reproduction of said auxiliary record and the ture coils of said rotor, and switching means for intervening to revise said auxiliary record during the reproduction thereof.

13. In an electrical transmission system including a volume control means inI circuit with a preliminary amplifier having a primaryl output circuit including monitoring means. means for the'automatic control of the transmission of said primary circuit in accordance with a schedule detcrmined in preliminary monitoring including a directcurrent motor having a rotor coupled to said volume control means and provided with armature coils, a pair of additional output circuits in said preliminary ampliiier, one of'said additional circuits including means for making an auxiliary record of said preliminary monitoring, theother of said additional circuits including amplifying means for' reproducing'the output ofsaid preliminary amplier and forrectifying said output, means for reproducing said auxiliary record including means for rectifying the currents reproduced from said auxiliary record, switching means selecting in a rst switch position said one additional circuit for making said auxiliary record and selecting in a second switch position said other additional circuit simultaneously with said means for reproducing said auxiliary record and impressing the rectified reproduction of said auxiliary record and the rectied output o f said other additional oricuit simultaneously and in opposition upon the armature coils of said rotor, and switching means for intervening to revise said auxiliary record during the reproduction thereof.

14. In an electrical transmission system including a volume control means in circuit with a preliminary amplifier having a primary output circuit including monitoring means, means for the automatic control of transmission of said primary circuit in accordance with a schedule determined 'in preliminary monitoring including a direct curoutput, means for reproducing said auxiliary record including means for rectifying the currents reproduced from said auxiliary record, and switching means selecting in a rst switch position said one additional circuit for making said, auxiliary record and selecting in a second switch position said other additional circuit simultaneously with said means for reproducing said auxiliary record and impressing the rectified reproduction of said auxiliary record and the rectied output of said other additional circuit simultaneously and in opposition upon the armature coils of said rotor,

15. In an electrical transmission system including a volume control means in circuit with a preliminary ampliiler having a primary output cirlcuit including monitoring means, means for the automatic control of transmission of said primary circuit in'accordance with a schedule determined in preliminary monitoring including a direct current motor having a rotor coupledto said volume control means and provided with armature coils, a pair of additional output circuts in said preliminary amplier, one of said additional circuitsincluding means for making an auxiliary record of said preliminary monitoring, the other of said additional circuits including amplifying means for reproducing the output of vsaid preliminary amplier and for rectifying said output, means for reproducing said y auxiliary record including means for rectifying the currents reproduced from said auxiliary record, and switching means selecting in a iirst switch position said one additional circuit for making said auxiliary record and selecting in a second switch position said other additional circuit simultaneously with said means for reproduclng said auxiliary record and impressing' the rectified reproduction of said auxiliary record and the rectified output ofsaid other additional circuit simultaneously and in opposition upon the armature coils of said rotor.

ARTHUR L. HoLcoMB. 

